Hows it going? Been reading posts for about 2 years, never had to post but this one has stumped me.

1989 2.8L 213K miles

Speedometer jumps (from speed to 0 to 30 to 0 .....) when I am off the gas. Most of the time jumps back to the correct speed when I get back on the gas. The odometer also stops when I am off the gas. Also if I am on a long trip say 30 minutes or more, the problem seems to go away

No code has been thrown (at least not 24, for some reason I got a 34 but thats a different issue).

I have changed the VSS, and speed buffer, checked the wires (seem ok but I am not an electrician), inspected the gears in the transmission (seem fine). I checked out the wiring to the guages and nothing seemed loose.

Any ideas? I am hoping not the ecm but I really dont have the equipment or one to put in to test.

Thanks for any replies

 

Try this question, ALSO, on the tranny side.
I THINK it's tranny related.
In my 1985? I lubed cable (w/axle grease, wrong stuff duh! oh well) and that stopped the jumping.
BUT because I didn't use PROPER white grease, I have this problem reoccuring, now.
Your problem is not this solution.
Does the Torque Convertor lock in & out, too?
Cause that is speedo related issue, also.
Was for me.

 

No problems with the torque converter (as I know of)

The car is in need of a timing chain replacement but other than that she is in pretty good shape.

Now back to the speedometer. I am thinking its a wire I missed or the ECM but could use any other ideas anyone might have. Since it is not throwing the code, wouldnt that mean the problem was between the ECM and speedometer? or am I thinking too much into this?

Thanks again

 

Is there a connection on tranny that needs or can be cleaned?
Have you removed dash, lately, to cause a loose wire?

 

You could ask on the general tech forum too; we have the same speedometer setup as the v8's do. Someone out there must've had this same problem.